Tirzepatide Dosage and Reconstitution Calculator

Missing a dose: what the label actually says

The Zepbound label gives a hard number that almost no secondary source reproduces: if a dose is missed, administer it as soon as possible within 4 days — 96 hours — of the missed dose. Past that window the instruction is to skip it and resume on the regular day. Nothing on the label supports doubling up to make the missed dose back.

The 4-day window tracks the drug's own pharmacokinetics rather than convenience. Tirzepatide's half-life is about 5 days, so a dose taken inside 96 hours arrives while a substantial fraction of the previous one is still circulating and the weekly rhythm survives. The three GLP-1 labels disagree with each other here, which matters if you have switched drugs: Ozempic allows 5 days, Zepbound 4, and Saxenda — a daily drug — instead says that if more than 3 days have elapsed you restart at 0.6 mg and escalate again. The rule does not travel with you.

Storage, and the point where the label stops applying to your vial

The approved product is stored in a refrigerator at 2°C to 8°C (36°F to 46°F). Each single-dose pen or vial may be kept unrefrigerated at up to 30°C (86°F) for a total of 21 days, after which it is discarded. It must not be frozen, must not be used if it has been frozen, and is kept in its original carton because the label directs that it be protected from light.

Every one of those figures came from stability testing on Lilly's own ready-to-use solution, and none of them transfers to a powder you reconstituted yourself. A compounded tirzepatide vial has no published stability data at all — not for the reconstituted solution, not for its life in a fridge, not for how long it tolerates a warm room. The 21 days is a fact about one specific manufactured product. Reading it as a fact about tirzepatide in general is the error the number invites, and it is the most common one on this topic.

What else is in the solution

The label lists the inactive ingredients in full: sodium chloride 4.1 mg, dibasic sodium phosphate heptahydrate 0.7 mg, and water for injection. What is absent matters as much as what is present — there is no antimicrobial preservative, which is precisely why every approved presentation is single-dose and why the label carries no instruction for storing a partly used one.

That is the same principle that governs the water you reconstitute with. A container entered once needs no preservative; a vial you will puncture repeatedly over several weeks is the case bacteriostatic water exists for. If you are drawing multiple doses from a compounded vial, the benzyl alcohol in that water is doing a job the approved product never needed done.

What the label reports as adverse reactions

Zepbound carries a boxed warning for the risk of thyroid C-cell tumours. It is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma or with multiple endocrine neoplasia syndrome type 2, and in anyone with known serious hypersensitivity to tirzepatide or to any of the excipients above.

The reactions reported at 5% or more, with the incidence ranges the label gives: nausea 25–29%, diarrhoea 19–23%, constipation 11–17%, vomiting 8–13%, abdominal pain 9–10%, dyspepsia 9–10%, injection site reactions 6–8%, fatigue 5–7%, and hypersensitivity reactions 5%. Hair loss, eructation and gastro-oesophageal reflux disease are each reported at 4–5%.

Those are trial figures for the approved product at approved doses, in monitored patients. They are not a prediction about a compounded vial whose actual content nobody has verified, and they should not be read as one in either direction — neither as reassurance nor as a ceiling.